Blender takes a long time syncing objects
This may not be a solution, but does help me speeding up the animation render. 

In my case one object needs a lot of time to synchronize. While this is happening the computer is not really busy. To use these ressources I started a 2nd instance of blender (background render at the commandline) starting rendering the 2nd half of the animation. This increased the render time of both render instances just a little bit which in general accelerates the animation render almost by a factor of two.

I don't know how that is influenced by the specific scene and the hardware used. But for me it worked pretty well.